Changing Duration for Cache Item Expiration Callback?

Question

Omar Alzabir Wrote In His Article:

" the minimum duration you can set for expire callback is 2 minutes. Although you can set a lower value, it does not work. Most probably the ASP.NET worker process looks at the cache items once every two minutes."

I tested it. the duration of delegate function callback was every 80 seconds not 2 minutes.
So is there any changes from .net2.0 to .net3.5 ??(because the article wrote at 2005).

How can I change this duration?

this is my cache Item Registration I fyou want to know:

    HttpContext.Current.Cache.Add(
        SomeCacheItemKey,
        "Test",
        null,
        DateTime.MaxValue,
        TimeSpan.FromMinutes(1),
        CacheItemPriority.Normal,
        new CacheItemRemovedCallback(CacheItemRemovedCallback));

was my Q clear?